Reduced baroreflex sensitivity and cardiorespiratory transfer in amyotrophic lateral sclerosis

Introduction: Clinically relevant autonomic disturbances have been reported for respirator-dependent ALS patients while subclinical involvement may be present in the early course. Methods: Eighteen patients with early-stage ALS and 18 age-matched controls were studied by means of standard autonomic tests (heart-rate response to deep breathing and tilt-table testing), and spectral analysis of heart rate (HR) and arterial blood pressure (ABP), using the associated transfer function as a measure of baroreflex sensitivity for the mid-frequency band (MF band, 0.05–0.15 Hz) and as a measure of cardiorespiratory transfer for the high-frequency band (HF band, 0.15–0.33 Hz). Results: Mean HR and ABP were increased in ALS, while results of standard autonomic tests were similar for ALS and controls. Transfer function analysis revealed reduced baroreflex sensitivity and diminished cardiorespiratory transfer during normal breathing. Conclusions: Cardiovascular autonomic functions are intact in patients with ALS. There is evidence of sympathetic enhancement and vagal withdrawal, accompanied by reduced baroreflex sensitivity.These findings are similar to those reported for essential hypertension and may point to a common central autonomic derangement in both disorders.